Stereoscopic graphics display terminals receive from a main or host computer image data that represent a physical object. The image data are generated by an application program such as, for example, a mechanical engineering computer-aided design program, which operates within the host computer. Typically, the application program generates three-dimensional image data corresponding to a three-dimensional representation of the object. Whenever they are rendered on a conventional two-dimensional display screen, the three-dimensional image data provide a single view of the object with perspective, hidden-line removal, shading, or other cues to assist an observer in visualizing the three-dimensional properties of the object.
Stereoscopic graphics display terminals require, however, stereoscopic image data that correspond to a stereoscopic representation of the object. The stereoscopic representation of the object comprises a right-eye view of the object and a left-eye view of the object. The right- and left-eye views are rendered on a two-dimensional display screen as a stereoscopic image and are directed toward an observer's right and left eyes, respectively. Since they represent only a single view of the object, the three-dimensional image data generated by the application program are incompatible with the operation of the stereoscopic display terminal.
One way to achieve compatibility between the three-dimensional image data and the stereoscopic display terminal is to configure the application program so that it generates stereoscopic image data from the three-dimensional image data. Such a configuration suffers, however, from at least three operational disadvantages.
First, generating stereoscopic image data by means of the application program consumes a relatively large portion of the valuable computing and data storage resources of the host computer. In particular, the stereoscopic image data corresponding to the right- and left-eye views of the object are formed by two complete sets of calculations and occupy about twice as much memory as does the three-dimensional image data.
Second, the host computer is typically operated in a multi-tasking format, thereby giving many users access to the host computer. As a consequence, the generation of the stereoscopic image data can be interrupted whenever an application having higher priority is run on the computer. In addition to delaying the formation of the overall stereoscopic image, such interruptions can also delay the rendering of portions of the right- and left-eye views, thereby causing the observer to experience "stereoscopic deprivation" and the eye strain resulting from it.
Third, image data are typically transmitted from the host computer to the display terminal in a serial format. The transmission of stereoscopic image data from the host computer to the display terminal would require a transmission period that is twice as long as that for three-dimensional image data. In the case of complicated objects, the duration of the transmission period for stereoscopic image data could be so long that it would interfere with the timing of the display of the right- and left-eye views of the object, thereby also causing the observer to experience stereoscopic deprivation.